Traditionally, much effort has been expended to improve the taste, color, odor or clarity of oral care compositions such as dentifrice (toothpaste), mouth rinse, and the like. Because of the nature of such compositions, the taste of a product may often be of more importance to consumers than the actual efficacy. Since many efficacious oral care components have undesirable taste, color, odor or clarity, efforts to improve these characteristics are common in the art.
It is highly desirable that consumer products for use in cleaning and care of the oral cavity impart a fresh and clean feeling as this provides consumers with a signal of continuing freshness and cleanliness. In addition to the feeling of cleanliness, consumers also want to experience the benefits of oral care actives like anti-microbial agents, for example, through their oral care regimen. The ability to formulate a consumer acceptable oral care composition, however, raises challenges as many of the components used to impart a flavor, deliver a benefit, or that are part of the base for the oral care composition add unwanted tastes and/or sensations along with the targeted benefit for which they are added. Thus, formulating oral care compositions can be a balancing act between acceptable flavor and acceptable benefits.
The sensations of bitter and sweet tastes are initiated by the interaction of sapid molecules (“tastants”) with G protein-coupled receptors (GPCRs) in the apical membranes of taste receptor cells (TRCs). TRCs are specialized epithelial cells with many neuronal properties including the ability to depolarize and form synapses. TRCs are typically clustered in groups of ˜100 within taste buds. The apical surface of TRCs, which makes contact with the oral cavity, is rich in convoluted microvilli containing GPCRs, ion channels, and other transduction elements. The basolateral aspect of TRCs contains ion channels and synapses with afferent taste nerves. Most sweeteners are small molecular mass compounds but a few sweet-tasting proteins have been described. Low molecular mass sweeteners and sweet-tasting proteins interact with the same receptor, as shown by recent, direct experiments: at least two of the well-characterized sweet proteins, i.e. brazzein and thaumatin, elicit a response in the human T1R2-T1R3 receptor, similar to that elicited by small molecular mass sweeteners. The sweet taste receptor is a heterodimer of two G protein coupled receptors, T1R2 and T1R3. Heteromeric T1R2:T1R3 taste receptors respond to sweet-tasting compounds such as sugars, high-potency sweeteners, and some D amino acids, whereas T1R1:T1R3 heteromers comprise a umami taste receptor sensitive to L amino acids [12 and 16]. Domains of human T1R2 and T1R3 are sufficient to confer sensitivity to some noncaloric sweeteners and sweet-tasting proteins to which rodents are indifferent, but it remains unknown which of these receptor subunits participates in the binding of most sweet stimuli, including sugars. G protein-coupled receptors mediate many other physiological functions, such as endocrine function, exocrine function, heart rate, lipolysis, and carbohydrate metabolism. The biochemical analysis and molecular cloning of a number of such receptors has revealed many basic principles regarding the function of these receptors. For example, U.S. Pat. No. 5,691,188 describes how upon a ligand binding to a GPCR, the receptor undergoes a conformational change leading to activation of a heterotrimeric G protein by promoting the displacement of bound GDP by GTP on the surface of the Gα subunit and subsequent dissociation of the Gα subunit from the Gβ and Gγ subunits. The free Gα subunits and Gβγ complexes activate downstream elements of a variety of signal transduction pathways.
Compositions taken into the oral cavity are first detected by taste receptors/channels and trigeminal neurons. This information is transmitted to the brain via trigeminal neurons and taste cells. Taste sensation is finally perceived in the brain as sweet, bitter, sour, salty, or savory. TRPA1 is a known, nonselective cation channel that belongs to the superfamily of Transient Receptor Potential (TRP) ion channels. The TRPA1 receptor acts to tell the human body that a substance in the oral cavity is unpleasant and should be expelled by conveying a pungent, bitter, unpleasant taste. A summary of the TRPA1 channel (as an emerging target for new analgesics and anti-inflammatory agents) with several of the TRPA1 agonists noted, is found in the article Transient Receptor Potential Ankyrin 1 (TRPA1) Channel as Emerging Target for Novel Analgesics and Anti-Inflammatory Agents, by Pier Giovanni Baraldi, et al, J. Med. Chem., Submitted Jan. 15, 2010. Of note, TRPA1 agonists such as citriol, eugenol, thymol, cinnamaldehyde (contained in cinnamon), eugenol, citral, geraniol, eugenol acetate, citral dimethyl acetal, or citral diethyl acetal, and certain flavorings used in oral care compositions typically express pungent, unpleasant tastes in the oral cavity.
However, many TRPA1 agonists are desirable in oral care compositions to provide other benefits. Therefore, there is a need to develop oral care compositions that contain materials that can bind to the TRPA1 receptor and yet provide a neutral or positive taste.
In US Patent Application No. 2008/0124753A1, it was disclosed that a taste profile can be created by dually activating two or more TRP receptors. Although A1 could be one of the receptors activated, the compositions of the '753 application required activation of two or more receptors simultaneously to create an acceptable flavor or taste profile and offered no solution for mitigating unpleasant tastes caused by TRPA1 agonists.
In US Patent Application No. 2008/0050750A1, a method was disclosed in which the TRPA1 receptor was deactivated by antagonistic molecules, in order to block the pungent taste of thymol and other lower alkyl phenols that bind to A1. Their system involved the application of molecules that would shut down an active TRPA1 receptor.
In US Patent Application No. 2009/0175848A1 it was disclosed to modulate (inhibit) TRPA1 ion channel activity by targeting the ion channel TRPM5 and vice versa through the cooperativity mechanism identified therein. More specifically, the US '848 reference disclosed modulating pain, mechanosensation, and taste responses triggered through the ion channels TRPA1 and TRPM5.
In US Patent Application 2008/0242740A1, vanillins and vanillin isobutyrate were generally disclosed as one of a series of compounds that gave rise to a sweet odor impression. The disclosed purpose of US '740 was to enhance the sweetness of chalcones via saliva stimulating agents and materials that give an initial burst of sweetness. No means were provided to remedy off-tasting components.
US Patent Application No. 2008/0317923A1 disclosed suppression of a bitter, astringent impression in the oral cavity via compositions containing saliva stimulating agents, bitterness-masking aroma substances and/or flavorings, of which vanillin esters were not disclosed. Ethyl vanillin isobutyrate was mentioned as a malodor suppressing agent, but was not disclosed as having an effect on off-tasting or bitter substances.
In US Patent Application No. 2009/0004360A1, oral compositions that provide an enhanced perception of an active substance were disclosed. In particular, the compositions included an active substance, such as a sweetener or flavor, and a sweetness modifier. The sweetness modifier was disclosed as increasing the perception of sweetness upon consumption. The compositions could be incorporated into various types of edible orally delivered products, such as beverages, food products, confectionary or chewing gum products. Vanillin isobutyrate was disclosed as a potential sweetness modifier.
Despite the known functionality of the TRPA1 receptor and standard binding materials, a need still exists for an oral care composition containing TRPA1 agonists and yet provide a neutral or positive taste.